Filter elements and additive containing material therefor



United States Patent 3,397,705 FILTER ELEMENTS AND ADDITIVE CON- TAINING MATERIAL THEREFOR Cephas H. Sloan and Bobby J. Sublett, Kingsport, Tenn., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Continuation-impart of application Ser. No. 425,920, Jan. 15, 1965. This application Aug. 2, 1965, Ser. No. 476,660

4 Claims. (Cl. 131-266) ABSTRACT OF THE DISCLOSURE A filter element and method of manufacture therefor wherein said filter element contains a tow material which comprises a bundle of fibrous filaments, said filaments having embedded therewithin and formed as an integral part thereof particles of a Water-soluble salt. The various salts are sodium phosphite and potassium phosphite and will chemically react with and thereby remove hydrogen cyanide from a gaseous medium.

This is a continuation-in-part of our copending application Ser. No. 425,920, filed J an. 15, 1965.

This invention relates to a tobacco smoke filtering material that is capable of selectively removing certain deleterious materials from the vapor phase of tobacco smoke. More particularly, this invention relates to a new fibrous type tobacco smoke filtering medium and a filter structure formed therefrom for selectively removing hydrogen cyanide from the vapor phase of tobacco smoke.

It has been known for some time that tobacco smoke contains certain deleterious materials including hydrogen cyanide that contribute nothing beneficial to the pleasant taste or aroma of the smoke. Thus, the problem which has plagued the tobacco industry for the last few years is how can an effective and practical tobacco smoke filter be fabricated which is capable of removing the deleterious materials produced when tobacco is smoked without at the same time adversely affecting the pleasant taste and aroma found in the smoke.

This search for a suitable yet inexpensive filtering medium which could be used with any tobacco product, and especially with cigarettes, led to the development of the so called fibrous filter units. These fibrous filter units, and particularly those made of cellulose acetate tow, have been found to be very effective for removing solid particulate matter, commonly referred to as tar, from the vapor phase of tobacco smoke. Certain undesirable gaseous components such as hydrogen cyanide which are found in tobacco smoke are not removed by such filters. Therefore it was proposed that certain gas adsorbing additives in the form of finely divided particles be dispersed within the fibrous filter unit for removing these undesirable gases. These particles of solid materials were generally placed on the surface of the filaments from which the fibrous filter unit was formed by adjusting or coating operation. Numerous solid adsorbing materials were tried with active carbon and certain silica gels being the ones most often used.

Although filters constructed in such a manner and which contain these various types of granular absorbent materials have been found to be effective to some extent in removing certain gases from the vapor of cigarette smoke, they nevertheless have inherent limitations and disadvantages which make the desirability of their continued use questionable. From a manufacturing standpoint alone the use of a finely divided material dusted onto a cigarette filter tow is undesirable because it (1) creates a house cleaning problem, (2) requires that extra 3,397,705 Patented Aug. 20, 1968 processing steps be included in the forming of the cigarette filters, and (3) necessitates that additional manufacturing equipment and time be used, all of which increases the expense of producing such cigarette filters.

However, perhaps the greatest single disadvantage of most of the various granular particels that have heretofore been suggested or used in cigarette filters is their inherent properties. For example, the adsorption characteristics of finely divided activated carbon is primarily dependent on the boiling point of the compound being adsorbed. That is, the least volatile vapors will be more readily adsorbed and retained better by activated carbon than the more volatile vapors. This is a definite disadvantage since several of the least volatile vapors in cigarette smoke are those which give flavor and taste to the smoke and are neither deleterious nor obnoxious. Therefore, the removal of these vapors is highly undesirable and if permitted to occur can result in what has commonly been referred to as a carbon or dry taste.

Although carbon filters do remove hydrogen cyanide, these filters are not selective. Other volatile gases which contribute taste and aroma to the smoke and are neither deleterious or obnoxious are also removed by carbon filters. Furthermore, the simple physical adsorption of vapors by a material like granular carbon in which no chemical reduction of the vapor occurs often results in at least a part of these vapors being again released at a later time, such as when the material is subjected to the heat produced as the tobacco burns cose to the embedded end of the filter.

According to the present invention it has been found that a fibrous fi-lter unit can be produced which is capable of selectively removing hydrogen cyanide from a gaseous medium of spinning the fibers of the filter from a rope of cellulose acetate which contains an additive of certain water-soluble inorganic salts. Since these inorganic salts are embedded in the cellulose acetate fibers as the fibers are being spun, the necessity of including additional processing steps, materials or equipment into the manufacturing operation is alleviated. The inorganic basic salts which have been found to be capable of selectively removing hydrogen cyanide from cigarette smoke are the sodium and potassium carbonates and phosphites. As will be apparent, these basic salts are capable of chemically reacting upon contact with the hydrogen cyanide gas to reduce the gas thereby assuring that the cyanide is not later released.

Therefore, an object of this invention is to provide a new and improved fibrous tobacco smoke filter unit.

Another object of this invention is to produce a fibrous tobacco smoke filter which is capable of selectively removing hydrogen cyanide from the smoke of tobacco through a chemical reaction technique.

Yet another object of this invention is to disclose a method of manufacturing a cigarette filter tow containing a water soluble inorganic salt.

Yet still another object of this invention is to describe a method of manufacturing a cigarette filter from a cellulost acetate tow that contains water-soluble inorganic salt which is capable of removing hydrogen cyanide from tobacco smoke.

These and further object and advantages of this invention will become more apparent upon reference to the following specification and appended claims.

It was commonly believed in the tobacco industry that a basic salt incorporated within a filament would be ineffective for removing hydrogen cyanide from cigarette smoke since the salt would be masked from coming into contact with the smoke by the material forming the filament. However, it has been found that certain groups of water soluble basic salts, if properly prepared, can be mixed with selected types of cellulose acetate dopes and spun to give a filament that readily neutralizes the hydrogen cyanide in tobacco smoke. The spinning solution or dope from which the inorganic salt containing filaments of the filter tow is to be spun can be produced in any one of several manners. In its broadest aspects, this is accomplished by adding directly to a cellulose acetate solution one or more water soluble inorganic salts selected from the group including sodium and potassium carbomates and phosphites. More specifical-ly, a finely divided powder of the selected group of water soluble inorganic salts 'which has been ground to pass through a 200 mesh screen is added to an acetone solution of cellulose acetate in the amount of 1 to 10 percent by weight. Although the amount of salt that can be added to the solution can be varied over a range of from 1 to 10 percent by weight, optimum results are obtained when only 2 to 5 percent by weight of the solution is the inorganic salt. After the water soluble inorganic salt has been added to the acetone solution of cellulose acetate, the mix is ball-milled to uniformly disperse the salt. The spinning solution containing the inorganic salt is now ready to be spun into filaments on a conventional spinning machine after which it can be formed into a tobacco smoke filter by any suitable manner.

From the foregoing description it is readily apparent that the water soluble inorganic salt containing tobacco smoke filter and tow of this invention offers numerous detoxicating advantages over those filters previously known and used in the cigarette industry. For example, not only is the filter a highly selective one which is capable of removing substantial amounts of the tar and hydrogen cyanide found in tobacco smoke as the smoke moves through the interstices of the filter, but the hydrogen cyanide removed is neutralized or reduced to a solid by-product which cannot later be eluted from the filter. Furthermore, the fact that the inorganic salt particles are embedded within the celluose filaments of the filter eliminates the sifting out and companion problems that have heretofore been present in filters containing solid additives. The method by which this filter tow is formed also alleviates the need for practically all the special equipment, processing steps and skilled personnel that has heretofore been required to produce filter tow having an additive therein. Thus the cost of producing the tow and filter units by the method of this invention is substantially reduced.

What is claimed and desired to be secured by the United States Letters Patent is:

' 1. In a method of manufacturing a cellulose acetate tobacco smoke filter unit which has embedded therein granules of an inorganic basic salt for selectively removing hydrogen cyanide from tobacco smoke, the steps of mixing together from to 99 percent by weight of cellulose acetate with from 1 to 10 percent by weight of an inorganic salt selected from the group consisting of sodium phosphite and potassium phosphite-spinning said mixture into a fibrous material, and forming said material into a gaseous tobacco smoke filter unit.

2. A tobacco smoke filter element comprising a bundle of continuous crimped cellulosic filaments which are generally oriented lengthwise of the filter element and extend from one end to the other thereof, said cellulosic filaments having embedded therewithin and formed as an integral part thereof particles of a basic water soluble inorganic salt selected from the group consisting of sodium phosphite and potassium phosphite.

3. A tow material which is adapted for use in forming a selective tobacco smoke filter unit, comprising a plurality of fibrous carriers arranged to form passages for the passage of gases therethrough, said fibrous carriers having embedded therewithin and formed as an integral part thereof particles of at least one water soluble salt selected from the group consisting of sodium phosphite and potassium phosphitewhich salt will chemically react with and thereby remove hydrogen cyanide from tobacco smoke within said passages.

4. The selective filter unit of claim 3 wherein said fibrous carriers are cellulose acetate filaments.

References Cited UNITED STATES PATENTS 2,172,946 9/1939 Sutter 131-265 2,956,329 10/1960 Touey 131266 X 3,019,794 2/1962 Whittnore et al 131-266 3,101,723 8/1963 Seligman et al 131269 X 3,173,427 3/ 1965 Tamblyn et al 131266 X 3,320,961 5/1967 Hughes et a1 131-267 2,832,351 4/ 1958 Hale 131-266 X 3,368,566 2/ 1968 Avedikian 13126S X FOREIGN PATENTS 760,772 11/ 1956 Great Britain.

SAMUEL KOREN, Primary Examiner.

D. J. DONOI-IUE, Assistant Examiner. 

